Final answer:
The approximate minimum alveolar concentration (MAC) delivered to a 50-year-old patient receiving 53% nitrous oxide and 0.9% isoflurane is approximately 0.75 MAC.
Step-by-step explanation:
The question asked is regarding the approximation of the minimum alveolar concentration (MAC) administered to a 50-year-old patient undergoing anesthesia with a specific mixture of gases. The MAC is a standard used to compare the strengths, or potency, of anesthetic gases. It represents the concentration required to prevent movement in response to surgical incision in 50% of patients.
The provided information states that the patient is receiving 53% nitrous oxide, 0.9% isoflurane, and 46% oxygen. To determine the MAC delivered, one must know the MAC values of nitrous oxide and isoflurane for a 50-year-old patient. Assuming the MAC for nitrous oxide is 104% and for isoflurane is 1.15% for middle-age adults (and does not vary significantly in the 50-year-old age range), we can use the following calculations:
MAC delivered = (Fraction of nitrous oxide / MAC for nitrous oxide) + (Fraction of isoflurane / MAC for isoflurane)
MAC delivered = (0.53 / 1.04) + (0.009 / 0.0115)
After performing the calculations, we find that the delivered MAC is approximately between 0.5 and 0.75, hence the answer is B. 0.75 MAC.